Why Bitcoin is trading at an all-time high: Read full story for latest details.

Bitcoin sounds like something from science fiction: A purely digital currency, created by an anonymous hacker, that operates outside the world's traditional banking systems. The four-year-old currency is very real, though, and it's trading an all-time high, tripling in value in the last two months alone. One bitcoin is was worth about $40 U.S. dollars on Tuesday, and surged on Wednesday to nearly $49. That's up from around $13 in January, and 5 cents in 2010, according to Mt. Gox , the bitcoin market's main exchange. On that and other trading sites, buyers can swap their digital coins for cold, hard cash. Watchers of the alternative currency attribute some of bitcoin's rise to the recent decision by several popular-in-geek-circles vendors to accept the coins -- most notably, blog hosting site Wordpress and the online community Reddit . "These guys are killing it on retail,...